Mn and Zn-Doped Multivariate Metal-Organic Framework as a Metalloimmunological Adjuvant to Promote Protection Against Tuberculosis Infection

A first-in-class vaccine adjuvant delivery system, Mn-ZIF, was developed by incorporating manganese (Mn) into the zinc-containing zeolitic-imidazolate framework-8 (ZIF-8). The mixed metal approach, which allowed for tunable Mn doping, was made possible by including a mild reducing agent into the reaction mixture. This approach allowed up to 50% Mn, with the remaining 50% Zn within the ZIF. This multivariate approach exhibited significantly decreased cytotoxicity compared to ZIF-8. The porous structure of Mn-ZIF enabled the co-delivery of the STING agonist cyclic di-adenosine monophosphate (CDA) through post-synthetic loading, forming CDA@Mn-ZIF. The composite demonstrated enhanced cellular uptake and synergistic activation of the cGAS-STING pathway, producing proinflammatory cytokines and activating antigen-presenting cells (APCs). In a preclinical Mycobacterium tuberculosis (Mtb) model, CDA@Mn-ZIF formulated with the CysVac2 fusion protein elicited a potent antigen-specific T-cell response and significantly reduced the mycobacterial burden in the lungs of infected mice. These findings highlight the potential of CDA@Mn-ZIF as a promising adjuvant for subunit vaccines, offering a novel approach to enhancing vaccine efficacy and protection against infectious diseases such as tuberculosis.